Submicron thick palladium-silver alloy films with 23 wt.% of silver (Pd-Ag23) have been synthesized by simultaneous sputtering from pure tat-gets of Pd and Ag. Full characterization of the deposited films was performed by using X-ray photoelectron spectroscopy, high-resolution scanning electron microscopy, high-resolution transmission electron microscopy, and X-ray diffraction. The analytical results revealed that the deposited Pd-Ag alloy had a Ag content of about 21-22 wt.%, very close to and within measurement error of the expected Ag content of 23 wt.%. The as-deposited Pd-Ag alloy had a fine microstructure. The characterized Pd-Ag alloy films were then deposited on a supporting microsieve to form Pd-Ag membranes for hydrogen separation. The submicron thick Pd-Ag membranes obtained high separation fluxes tip to 4 mol H-2/m(2) s with a selectivity higher than 1500 for hydrogen over helium. (c) 2004 Elsevier B.V. All rights reserved.